The present invention relates in general to cathode sputtering equipment and in partiular to a new and useful target plate therefore.
Target plates for cathode sputtering consists of a material which is to be disintegrated in a cathode sputtering apparatus in order to precipitate on substrate surfaces a layer of the respective material or, in the presence of a chemically active residual gas in the sputtering apparatus, a chemical compound of the target material with an active gas.
In installations of relatively high power, the cathode plates are often exposed to a very high thermal load due to bombardment with ions and must be cooled to remove the excess thermal energy. Nevertheless, at high power the problem arises that when the target plates are rigidly clamped at their rim, as usual, while being pressed against a cooled support, they warp as a result of thermal expansion and will then lift off the support, causing the cooling to become insufficient and the target material to assume too high a temperature. It will then soften and may possibly even melt in the end. To prevent this, it has been tried to solder or weld the back of the target plate to the cooled support. Such a union had to be made extremely carefully, however, as otherwise the target plate could become detached from the support nevertheless. At any rate, this soldering on or welding is laborious. Usually the edge of the target plate was screwed tight on the cooled support, and also in the center of the plate a screw attachment was provided to prevent it from lifting off. Also there has been proposed a target plate with several cutouts along a parallel center line of the surface to be disintegrated, these cutouts being disposed in the bottom of a groove applied on the side of the surface to be disintegrated, along the center line, and the groove depth is dimensioned so that a bar inserted in the groove for the attachment of the target plate and the respective attachment screws do not protrude over the disintegration plane.
Owing to the thinness of the target plate in the area of the groove bottom in the center of the plate, where in earlier arrangements usually the highest temperature occurred during the sputtering, improved cooling was achieved at this point, thus preventing the material from warping or flowing in the regioin of the center attachment. The need for an attachment bar on the front of the target plate, that is, on the surface to be disintegrated, still constituted a disadvantage, however, in particular if even the least concomitant disintegration of the material (steel) of which the central attachment bar and the attachment screws were made, impermissibly contaminates the layers to be produced.